Supernatural Lucifer
by las2217
Summary: Supernatural/Lucifer crossover. Getting rid of the Mark of Cain shook more than just the Supernatural universe and the Darkness wasn't the only thing that fell free. A very confused Lucifer suddenly finds himself in the wrong place and is drawn to the bunker where he meets Sam, Dean, and Cas.


**Author's Note:** Hey y'all. So, I don't necessarily consider this one of my best works, but I filled a prompt for a Supernatural/Lucifer crossover (I'm still my own biggest critic, plus this is my first attempt at a crossover of any sort, so of course I'm thinking it's horrible. Oh well. Lol). It's set early Season 11 when Cas is still under Rowena's "attack dog" spell. I'm pretty sure I completely ran out of talent with this one, hence the lack of a real title as well. I'd love to hear opinions on it/suggestions for a title if it's any good. :)

 **Prompt:** Lucifer from 'Lucifer' gets sucked into the SPN world and runs across the Winchesters. When his Cas was a fledgling, Lucifer had tons of fun teaching him to be naughty until Michael (boring) put his foot down.

So even though he knows this isn't his Cas, it still causes him anguish to see how run down Cas is. He decides he's saving his little brother, and begins to take care of Cas, getting him back on his feet and amusing himself by flirting with Sam - not getting that the SPN Lucifer has tortured Sam until Cas tells him to knock it off - and sassily dressing Dean down for not taking better care of his angel.

The Winchesters aren't sure if this Lucifer is worse than theirs.

* * *

~ Supernatural/Lucifer ~

"What the bloody hell is going on?" Lucifer looked around himself. Just moments ago he'd been getting ready to go downstairs and put in an appearance at Lux. Then he'd felt the ground move and had just enough time to curse California and it's propensity for earthquakes before darkness overtook him and he suddenly came to, standing on some abandoned back road in what appeared to be the middle of nowhere.

Well, standing there in the road until the end of time wasn't apt to get him any answers, so he started walking. He only made it a few steps before a feeling shot through him that made him turn and start quickly in the other direction. An angel was hurt. And unless he was mistaken, not just any angel. Castiel.

Less than five minutes later, Lucifer came around a bend in the road to see a set of stairs leading down into what looked like some underground bomb shelter. It wasn't any sort of bomb shelter he'd ever seen before, though. It was warded against damn near everything as far as he could tell. He could feel it and Castiel's grace radiating from inside though, which mean his brother was in there somewhere. Without hesitating he reared back and kicked the heavy door in.

"I wouldn't have done that if I were you," flashing green eyes and a cocked pistol belied the casual tone of voice that the blonde man at the bottom of the stairs had used.

Lucifer just grinned. Without the detective nearby he had no reason to worry about some human threatening him with a gun. Under different circumstances, he might have taken a moment to admire the man holding a gun on him. Tall, green-eyed, blonde, freckled, handsome…the list could go on and on. At the moment, the pain he could feel coming off of Castiel in waves was his only concern though.

"Tell me where my brother is and I might consider killing you quickly," he offered.

"Funny, that's usually my line," Dean kept his gun levelled on the man stalking down the stairs. "Counter-offer. Turn around and leave now and I might consider letting you go alive."

"Give it your best shot," Lucifer taunted as he reached the bottom of the stairs and stepped right into Dean's personal space. "Really. It's been a long time since I've had the proper motivation to torture someone and being shot might be just the push I need."

"Dean," Cas's voice called weakly from the adjacent room, making both Dean and Lucifer turn.

Lucifer took one look at Castiel, sitting shackled to the floor, and lost whatever semblance of patience he had been hanging onto. He roared and lunged for Dean, knocking the gun out of his hand. He grabbed the blonde man by the throat and pinned him against the wall, letting his eyes flare and showing his true face.

Unlike the pure terror reaction he was used to getting, Dean only looked at him disgustedly.

"What are you? Some new type of demon?" he asked. "One that's somehow unaffected by devil's traps and warding? And butt-ugly to top it off?"

"A demon?" Lucifer laughed. "Oh no. I'm much worse. Some people like to call me the devil. I prefer my actual name. Lucifer."

"Lucifer?"

Finally! Finally there was an expression on Dean's face that wasn't sarcasm, disgust, or some type of bull-headed stubbornness. Lucifer almost had time to enjoy the change before he saw a glint of silver that made him back quickly away.

His first reaction was to wonder what type of people these were that they knew about angels and demons and warding. His second reaction was to gape at the new, ridiculously tall man standing in front of him wielding an angel blade. The blonde man had been more than easy on the eyes, but this one…

"Sam! Dean! Wait," Castiel had managed to struggle to his feet, although the shackles kept him from being able to move more than a few feet towards them.

"Wait for what, Cas?" Sam demanded. "It's Lucifer! I don't know how he got out of the Cage, but I'm damn sure not gonna wait around to ask him nicely to explain it."

"Cage?" Lucifer tilted his head to the side. "What's the Cage? Is it some new club I haven't heard about yet?"

"What?" Dean caught his breath back and moved to stand in front of Sam.

This made absolutely no sense. First Lucifer barged in, acting like he had no idea who they were. Now he was talking like he didn't know about the Cage. The only thing Dean could figure was that Lucifer had finally snapped down there, being locked up for so long.

"This isn't the Lucifer from our universe," Cas said, as if it was the most normal thing in the world. "He's a version of Lucifer, yes. But not the one we've dealt with in the past."

"Okay, let's pretend like any of that made sense," Dean wasn't even entirely sure that Cas knew what he was saying. Rowena's curse had really done a number on him.

"Cassie?" Lucifer took a step towards Cas and immediately got two angel blades in his face for his troubles. "Would you two stop that? I wouldn't hurt my own brother."

"Bullshit," Sam growled. "You would and you have. And he's not the only one."

"Well, I can't change whatever my doppelganger may have done to you, but I can certainly try to make up for it," Lucifer offered with a lewd grin at Sam.

Sam paled, but stood his ground. It wasn't bad enough that his hallucinations of the Cage had come back? Now he had to actually deal with Lucifer on top of it? The more he talked, the more it was obvious that this one was definitely different from the one they were used to, but he wasn't sure if he was different in a good way, a bad way, or just…well, different.

"No thanks," Sam finally spat out.

"Is he always such a prude?" Lucifer asked, pushing his way past the brothers to kneel next to his own. "What's been done to you?"

"A very powerful witch," Cas said by way of explanation, slumping down in his chair.

"Well leaving you chained to the damn floor is no way to get you better!" Lucifer turned a disapproving glare onto Sam and Dean. "Come now. Where's the nearest bed in this mausoleum?"

"I don't remember offering to let you stay," Dean snapped.

"I don't remember offering to leave," Lucifer shot back. "Which of you two boneheads is responsible for allowing a witch to curse my brother?"

"Neither of us 'allowed' a witch to curse him," Dean said defensively. "Shit just happens sometimes. If we could've been there, we would've."

"And what, may I ask, was so much more important?" Lucifer demanded, eyes blazing at Dean again. He didn't like the way the blonde man was acting all defensive of Castiel.

"Trying to get rid of the Mark of Cain," Sam put in. "We needed the witch to cast the spell to get it off of Dean's arm, and she turned on us."

"Trying to…" Lucifer looked at the two brothers, dumbfounded. "Is that what…Cassie, please tell me this is all some sort of a bad joke?"

"No, It's no joke," Cas said, tilting his head to the side. He was confused as to why the Mark of Cain would be something funny anyway.

"I'm getting him somewhere he can properly rest and then we three are going to sit and have a chat," Lucifer's tone left no room for argument as he ripped the chain free of its hook in the floor and wrapped an arm around Cas's shoulders.

Cas pointed him further into the bunker, but hesitated once they reached the new hallway.

"I don't usually rest," he admitted. "I don't have a room."

"What about blondie's room, then?" Lucifer suggested with a wink. "I don't think he'd mind sharing."

"Dean?" Cas looked surprised. "No…um, no."

"The tall one then?"

"No!" Cas said even more forcefully. "Sam and Dean are my friends. Nothing more."

"Pity," Lucifer commented. He opened the door closest to where they were standing at the moment, which of course just so happened to be the door to Dean's room. "This one looks like it will do nicely."

He deposited Cas on the bed and started fussing around the room, getting him settled. Clearly whoever Sam and Dean were, they weren't taking very good care of the angel on their shoulders and damned if he wasn't going to have something to say about that once he got back out there.

"So, Cassie," Lucifer chatted as he found pillows to prop around his little brother. "Tell me what sort of antics you and I got into in this universe."

"Antics?" Cas asked. "

"Yes," Lucifer prodded. "When the Castiel of my universe was just a fledgling I had so much fun teaching him all sorts of infuriatingly naughty pranks and antics. He, Gabriel, and I were nearly inseparable for a time. Until that bloody bore Michael decided that I was a bad influence on both him and Gabe."

Cas hesitated for a moment. Not only had none of that ever happened in this universe, apparently in Lucifer's time Gabriel was still alive. He had to find a way to break both bits of news to him.

"I'm afraid that the Lucifer of this timeline and I, we weren't close," Cas admitted. "Nor were Gabriel and I overly close, although he became a valuable ally."

"Why all the past tense…?" Lucifer broke off as he processed. "Oh."

"This universe was put through the beginning stages of the Apocalypse," Cas explained. "There were…casualties before we were able to stop it. Gabriel was one."

Sam and Dean crept towards Dean's room as quietly as they could manage while Lucifer and Cas talked. Neither of them trusted this Lucifer any more than they had trusted the last one. Personally, Dean had no intention of leaving Cas alone for too long with the Devil anyway. Purely because he was worried about his friend, of course.

"What the hell, Sam?" Dean whispered.

"I don't know," Sam shook his head.

"No, seriously. What the hell?" Dean repeated.

"I don't know!" Sam hissed again. "I mean, obviously this isn't 'our' Lucifer. There's no way he could've gotten out of the Cage. Did you see the look on this one's face when we mentioned getting rid of the Mark of Cain, though?"

"You think that could have something to do with why he got dropped out of his own universe and into ours?" Dean asked.

"Best theory I have so far," Sam shrugged. "Question is, how do we get him back? One Lucifer per universe is enough for me."

"I could do without even that many," Dean muttered. "Where do we even start looking for ways to…"

"I am an archangel, you know," Lucifer informed them, stepping into the hall and shutting the door firmly behind him. "It'll take a lot more than whispers to keep me from hearing what you two are planning."

"Not like it's much of a surprise anyway," Dean stood his ground, staring defiantly into Lucifer's eyes. "You already knew we wanted you gone."

"Yes, I did," Lucifer seemed to consider for a moment before a sly grin made its way across his face. "I know that's one of the things you want, but what is it you truly want? What you truly desire?"

"What are you talking about?" Sam wondered.

"Cas," Dean answered at the same time. "What I really want is Cas, but I've always been too afraid to actually say anything to him."

"Dean?" Sam was holding back laughter. Granted, it wasn't like he was surprised at Dean's admission, just the fact that he'd actually made it.

"What the hell was that?" Dean clapped a hand over his own mouth. Better late than never, he guessed.

Lucifer had raised an amused eyebrow at Dean's claim, but most of his focus was on Sam. Up until this point the only person who'd ever been able to resist his question was Detective Decker. It seemed like this Sam was another wild card. He wondered if he'd also be vulnerable around him the way he was around Chloe.

"Odd," he mused, staring intently at the gigantic man. He reached out to fiddle playfully with the collar of Sam's plaid over shirt. "I really must explore you a bit more."

Sam recoiled away from him, almost tripping over his own feet.

"Touch my brother again and I swear I'll enjoy every second of the torture I put you through," Dean warned.

"You can't even take care of an angel. What makes you think you can take on an archangel?" Lucifer taunted.

"Oh I learned plenty from Alastair during my time downstairs," Dean's voice lowered into a growl. "I might not be able to break you, but I'll have a hell of a lot of fun trying."

"Alastair? That second-rate, poor excuse for a demon couldn't torture the skin off of a hairless cat," Lucifer laughed. "If you want a real lesson in torture, I'd be happy to show you. Using you as the guinea pig, of course."

"Enough!" Sam yelled. "Can we please stop playing 'who's dick is bigger' and figure out how to get you out of here and back to where you belong?"

The minute he said that Lucifer's grin widened even more. Sam replayed what he'd just said and groaned. He'd just left himself wide open for…

"If we're playing that game, why don't we end the suspense and 'show what we've got' so to speak?" Lucifer suggested.

"I'm going to check the digital log I made up of this place," Sam quickly bolted down the hall towards his own room. "See if I can find anything that'll send your ass back to where you belong and see if I can track down a way to get rid of Cas's curse."

"I'll go pick up food and beer," Dean grumbled. He knew he should probably be helping with the research, but he sucked at it and he usually just wound up either frustrating Sam or getting bored and looking at porn, which also frustrated Sam.

"Then I'll take care of Castiel, since I'm the only one here who seems to know how to do that properly," Lucifer let himself back into the room.

"You should go easier on the both of them," Cas scolded the minute he walked in.

"They're such fun to tease, though," Lucifer argued. "They're both so easy to torment."

"Sam and Dean have their reasons for being the way they are," Cas said vaguely.

"Speaking of the way they are, why is it that Sam seems to be immune to my powers?" Lucifer dragged the desk chair over and sat next to the bed. "They worked beautifully on Dean, but I've only ever seen one other human who they didn't work on and she's a bit…special."

"It's most likely because Sam is the true vessel of Lucifer in this universe," Cas explained. "He is the one who stopped the Apocalypse. He allowed Lucifer to possess him and then jumped into the Cage with both Lucifer and Michael."

"What's this Cage you've mentioned?" Lucifer wondered. "This is the second time I've heard of it, but I don't understand."

"When God cast Lucifer out of Heaven, He created a Cage down in Hell," Cas told him. "A Cage where Lucifer would be bound for all eternity unless sixty-six seals were broken and the Cage was opened. When Sam jumped into Hell, bringing Lucifer and Michael along with him, he trapped himself in the Cage with them. What happened to him, what Michael and Lucifer did to him down there, was nothing short of the worst kind of torture imaginable."

"That's why he's so scared of me," even though it hadn't been him, Lucifer felt guilty. He also felt guilty for brazenly flirting and throwing himself at the man who was clearly terrified of him. If he'd bothered to stop and think about it for a second, he would've seen that.

"Dean is a good man also," Cas added. "He sold his soul for his brother, took on the Mark of Cain to defeat a Knight of Hell, and helped to save the world."

"Look at you, sticking up for your sweetheart," Lucifer joked. It was already obvious that Cas had overheard their entire conversation in the hall. No point in pretending he hadn't heard that part as well.

"Dean and I are friends, nothing more," Cas repeated his statement from earlier.

"He wants there to be something more though," Lucifer reminded him.

"Regardless, we're only friends."

They went around in circles on that topic for several minutes until the door suddenly burst open, Sam and Dean talking animatedly.

"I know where Rowena is!" Dean crowed, waving a newspaper around.

"You do not know where Rowena is!" Sam argued. "Just because something weird and very witch-like happened at a restaurant doesn't mean it was her."

"Sammy, come on," Dean rolled his eyes. "Witnesses are saying that some red-headed woman stacked a whole bunch of furniture without ever laying a hand on it to cover her escape. That's obviously witch behavior and how many red-headed witches do you think are floating around out there on their broomsticks?"

"They don't actually ride broomsticks, Dean," Sam rolled his eyes right back at his brother. "Give me a couple of hours and I'm sure I can find some way to break this curse. Unless you can do it?"

Sam and Dean both looked hopefully at Lucifer. Neither of them particularly wanted to deal with Rowena again so soon.

"Sorry boys," Lucifer shrugged. "Cut my wings off and burned them when I decided I was done with Hell for good."

"That sounds painful," Sam winced.

"Extraordinarily so," Lucifer caught himself just in time before he offered to take his shirt off to show just how bad the scars were.

"Looks like we're going after Rowena, then," Dean said.

"Come on, Dean. This paper is from yesterday," Sam pointed out. "Rowena's had at least twelve hours since this happened. She could be halfway around the damn world by now."

"Well I may not be much use to heal anyone, but I can at least find one puny witch," Lucifer offered.

"Why?" Sam and Dean asked at the same time.

"Let's just say that Cassie has brought some things to my attention that changed my outlook on you two," Lucifer answered. "Give me five minutes and I'll make sure you've got a location on this witch."

With that he strode confidently out of the room. After a moment of hesitation, Sam followed him, leaving Dean to take care of Cas.

"Seriously, why are you helping us?" he asked.

"Castiel is my brother," Lucifer reminded him. "Helping you is a way to help him. More than that, though. He explained some of the things that you and that thick-headed brother of yours have done. I may think you're idiots, but you're apparently semi-capable idiots."

"He obviously didn't tell you enough about us, then," Sam muttered. "We tend to 'fix' one thing that causes something else to happen that's ten times worse."

"Yes, the Mark of Cain," Lucifer looked around. "Where in the bloody hell can I find a prism, or at least a mirror in this maze? You mentioned something before about getting rid of the Mark of Cain from your brother. Since I'm assuming he didn't transfer it, that means darling Auntie Amara should be running loose about now, yes?"

"Aside from the snark, that about covers it," Sam pointed in the direction they should go. "We don't know where she is, either."

"Is there ever a time when you do know where someone is?" Lucifer wondered. "Ah! A mirror. This should do nicely."

Back in Dean's room, he took over the chair that Lucifer had vacated.

"Cas," Dean started.

"Dean," Cas said at the same time.

They looked at each other and then quickly dropped their eyes. Cas motioned for Dean to go first.

"Okay, uh, I guess…I guess you probably heard the conversation from before, huh?" Dean asked.

"I did."

"Right. I just, I don't want that to make things weird with us, you know?" Dean suddenly found a hole that had started in the knee of his jeans fascinating.

"No, it won't be 'weird' between us," Cas assured him. "I know that it was Lucifer's power making you say that anyway."

"Yeah! Exactly!" Dean jumped at the suggestion. "Good, I'm glad we got that covered. One crisis averted, am I right?"

Cas nodded and both decided that staying quiet until Sam and Lucifer came back was probably for the best. It would keep both of them from admitting what they really felt, anyway.

~ Supernatural/Lucifer ~

"Come now, boys. Is this really completely necessary?" Rowena complained as Sam and Dean dragged her into the bunker, magic cancelling handcuffs securely in place.

They'd caught up to her getting ready to skip town, blonde wig securely in place. She'd tossed Dean around a bit, but Sam had come up behind her and gotten the cuffs around her wrists.

"I mean, what's a bit of fun among friends, anyway?" Rowena continued.

"We are not friends," Dean growled.

He dragged the witch to where Cas was still laid up in his room and slammed her down into the chair that was still next to the bed. Unfortunately Cas was in his own set of cuffs and shackles once again. It had nearly killed Lucifer, but Cas had gotten out of hand while the brothers were gone to retrieve the witch. The curse had taken hold and he'd tried to escape out of the bunker and Lucifer had had no choice but to restrain him. Now Cas was curled up into a tiny ball on the bed, writhing in pain.

"Lift the curse," Sam ordered.

"He's cute like this, though!" Rowena argued. "He's like a wee attack dog."

"He wasn't asking and neither am I," Lucifer stepped forward.

"And who might you be?" Rowena asked.

"Lucifer," he answered honestly. "Now fix my brother so I can get on with killing you."

"Really now? Well that's no way to get what you want," Rowena sat back in the chair and crossed her arms primly. "If you're going to kill me either way then there's really no point in me healing the angel."

"Lucifer, back off," Dean ordered. "How about this? You heal Cas or you can spend the rest of your life in the dungeon downstairs, in those cuffs. And we both know that the rest of your life is a long, long time."

"Very well," Rowena tried to act casual, but there was a distinct note of fear underneath that pretend calm exterior. A few words of Latin later, Cas slowly uncurled himself, panting.

"Cas?" Dean lurched forward. "You good? You with us?"

"I'm better than I was," Cas admitted.

"So? Your end of our bargain?" Rowena raised one sculpted eyebrow.

"About that," Dean moved to stand directly in front of the witch. "We're gonna need one more thing from you before we let you go. The Book."

"The Book was not part of the agreement," Rowena gritted her teeth.

"It is now," Dean shrugged. "Unless you like the idea of spending the rest of your life in chains."

"Ugh, I should know by now to never trust a Winchester," Rowena sighed. "Never willing to keep their end of the bargain."

"What?" Dean asked.

"Why don't you ask your brother what I mean?" Rowena suggested.

"Sammy?"

"Shut up!" Sam snapped. "She's a liar, Dean. You know she'll say anything to pit us against one another."

"Except why do I get the feeling you're keeping secrets? Again," Dean's hands rolled themselves into fists.

"Just as I thought," Rowena said smugly. "Dear Samuel didn't tell you about our deal. I get rid of the Mark of Cain from your arm, he kills my son. It was a straightforward enough deal, and you're now free of the Mark, but is Fergus dead? No!"

"We will talk about this later," Dean snarled at Sam. He turned back to Rowena. "Right now I'm concerned with you, though. We found the codex in your things, but not the Book of the Damned, so hand it over."

"My dear boy, do you really think there's any way I would keep those two items anywhere near one another?" Rowena laughed. "Those two incredibly powerful items?"

"Fine, it's not here. Tell us where it is," Dean was definitely losing his temper.

"Somewhere you will never find it," Rowena ground out. "Keep me here if you must, but one day in the very near future I will get free and when that day comes…"

She broke off and let the threat hang. Lucifer muttered something under his breath and pushed Dean out of the way to take his place standing right in front of the witch. He leaned down so they were eye-to-eye.

"Tell me, witch, what is it that you truly desire?" he asked.

"To be the strongest witch in the world," Rowena answered without hesitation. "To be greater than the Grand Coven ever could have dreamed and make them regret ever tossing me to the wayside."

"And how do you plan on achieving that?" Lucifer asked.

"By using the Book of the Damned, of course," Rowena laughed.

"Which would be where?"

"A safe deposit box," Rowena answered. "At a bank in Topeka, under the name Olivia Callahan."

Lucifer finally straightened back up and smirked as Rowena's eyes widened.

"That's where your Book of the Damned is," Lucifer said to Sam and Dean. With that, he reached casually out and snapped Rowena's neck.

"What the hell!" Dean shoved Lucifer away a second too late. He reached out to test for a pulse, although that was just a formality. "Why did you kill her?! She was the only one who could decipher that Book, which was our only shot at getting Amara back to wherever she came from, and you just snapped her neck!"

"She was annoying," Lucifer shrugged, bored. "Besides, I can assure you that you need more than just a book to lock the Darkness back up. Which is where I come in."

"You?" Sam asked.

"Do you two know nothing?" Lucifer sighed. "Who do you think helped Father lock her up to begin with? You need me."

"No, absolutely not," Dean said. "We're finding a way to get you back to your own universe and we will deal with putting Amara back."

"Dean," Cas spoke up hesitantly. "Perhaps he's right. We need as much help as we can get in this fight against the Darkness."

"I agree with Cas, Dean," Sam couldn't believe what he was saying. "I, uh, I have to come clean about something."

"Yeah, now you decide to be honest," Dean snapped, still pissed about the secret Rowena had mentioned.

"I deserved that," Sam winced. "Lately I've been…having visions of the Cage, of Lucifer."

"You what?!" Dean exploded.

"See, that's why I didn't say anything," Sam put his hands up defensively. "I knew you'd freak out. But I feel like maybe I was being given a sign of how to take care of Amara. Like maybe God was trying to tell me who we needed to help us lock her back up."

"That's crazy, Sam!" Dean growled. "No. We're not working with Lucifer!"

"Well I'm not seeing a lot of other options here!" Sam argued. "Besides, I haven't been able to find anything that might help us get him back to where he came from, so as long as he's here we might as well use him."

"It's Lucifer, Sam!" Dean reminded him, in case he'd forgotten. "You're talking about teaming up with Lucifer."

"If he's our best chance to get rid of Amara, then I say we put the past aside," Sam had to force the words out, even knowing that this Lucifer was different from the one he'd been trapped with.

Dean paced back and forth, not saying anything for a minute. He knew that Sam, Cas, and Lucifer were all watching him and waiting. No way did he want to work with Lucifer, but at the same time it wasn't like they had a ton of other options. Their research on things to use against Amara was turning up empty. Despite the fact that they now knew where the Book of the Damned was, the only person who could read it was dead. Crowley was in the wind, which meant there was no help from that end either. Dean growled and ran his hands through his hair in frustration.

"Fine," he ground out. "But if we're gonna work together, there's going to be ground rules in place and the second it's over, we find a way to kick you back to your own time and place."

"Agreed," Lucifer grinned. "So where do we begin?"


End file.
